title: The aquaporin-Z water channel gene of Escherichia coli: structure, organization and phylogeny.
abstract: Aquaporin water channel proteins are found throughout the plant and animal kingdoms, but the first prokaryotic water channel gene, aqpZ, was only recently identified in wild type Escherichia coli (Calamita G et al (1995) J Biol Chem 270, 29063-29066). Here we define the organization of aqpZ in E coli, produce the AqpZ protein and compare the AqpZ phylogeny to that of some known bacterial homologs. Physical mapping and sequence analyses confirmed the location of aqpZ at minute 19.7 on the E coli chromosome where it is transcribed counterclockwise. The monocistronic nature of aqpZ was clearly indicated by the structural organization of its surrounding genes, ybjD and ybjE' and by the presence of a typical Rho-independent transcriptional terminator following the aqpZ stop codon. Computer sequence analysis indicated the -35/-10 region located 72 bases upstream of the aqpZ start codon as the most likely aqpZ promoter. A series of potential cis-regulatory elements were found in the 400 bp region preceding the aqpZ ORF. The AqpZ protein, produced under T7 phi 10 control, showed a size of about 20 kDa by SDS-PAGE. Striking similarities were found between the E coli aqpZ and a gene included in the genome of the cyanobacterium Synechocystis sp PCC6803, a species permanently living a fresh water. These results may represent a fundamental step to characterize the regulation and the physiological features of the AqpZ water channel in prokaryotes.
authors.affiliation: Istituto di Fisiologia Generale, Università degli Studi di Bari, Italy.
authors.forename: G
authors.initials: G
authors.lastname: Calamita
authors.forename: B
authors.initials: B
authors.lastname: Kempf
authors.forename: K E
authors.initials: KE
authors.lastname: Rudd
authors.forename: M
authors.initials: M
authors.lastname: Bonhivers
authors.forename: S
authors.initials: S
authors.lastname: Kneip
authors.forename: W R
authors.initials: WR
authors.lastname: Bishai
authors.forename: E
authors.initials: E
authors.lastname: Bremer
authors.forename: P
authors.initials: P
authors.lastname: Agre
mesh_terms: D020346:Aquaporins; D001426:Bacterial Proteins / Q000235:genetics; D002874:Chromosome Mapping; D002876:Chromosomes, Bacterial; D000458:Cyanobacteria / Q000737:chemistry / Q000235:genetics; D004926:Escherichia coli / Q000737:chemistry / Q000235:genetics*; D029968:Escherichia coli Proteins; D015964:Gene Expression Regulation, Bacterial; D007473:Ion Channels / Q000235:genetics*; D008565:Membrane Proteins; D008969:Molecular Sequence Data; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014867:Water / Q000378:metabolism*
chemical_list: D020346:Aquaporins; D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D007473:Ion Channels; D008565:Membrane Proteins; C106425:aqpZ protein, E coli; D014867:Water